Prostate Specific Antigen Assay Standardization Bias Could Affect Clinical Decision Making
Department of Urology, The Johns Hopkins Medical Institutions, Baltimore, Maryland, USA. The Journal of urology
(Impact Factor: 4.47).
10/2008; 180(5):1959-62; discussion 1962-3. DOI: 10.1016/j.juro.2008.07.036
Although prostate specific antigen is widely used to detect and manage prostate cancer, many patients and physicians are unaware of which prostate specific antigen assay is being used. Most commercial prostate specific antigen assays are standardized to the WHO 90:10 standard or aligned with the original Hybritech assay with potentially disparate results.
A total of 1,916 men participated in a prostate cancer screening study in 2007. On the day of collection prostate specific antigen was tested from the same serum sample using the Access (Hybritech standard) and ADVIA Centaur (WHO 90:10 prostate specific antigen standard) assays. We examined the differences between the 2 assays and the effect that this might have on clinical decisions.
Median prostate specific antigen was 0.9 and 1.05 ng/ml for the Centaur and Access assays, respectively, representing a 17% difference. Mean prostate specific antigen was 3.45 and 4.79 ng/ml, respectively, representing a 38% difference. Using a prostate specific antigen threshold of 2.5 ng/ml 5% of men would have been recommended to undergo biopsy using the Access but not the Centaur assay. Furthermore, prostate specific antigen differed by greater than 0.4 ng/ml in 26%, greater than 0.75 ng/ml in 14.5% and greater than 2 ng/ml in 4.5% of men in the same sample simply by using the different assays.
In our prospective screening population median prostate specific antigen was 17% lower using WHO vs Hybritech based assay standardization. As such, if these assays were instead used on a serial basis in the same patient, this could lead to false acceleration or false deceleration in prostate specific antigen velocity. Thus, the assay may influence the likelihood of prostate biopsy and, thereby, prostate cancer detection.
Available from: Judd W Moul
- "Drawbacks of PSA as a screening test include the diagnosis and treatment of some indolent tumors that would not have presented clinically and limitations in specificity whereby serum PSA levels may be elevated in benign prostatic conditions (benign prostatic hyperplasia, prostatitis) and urinary tract manipulation (eg, cystoscopy, prostate biopsy) . In addition, recent studies have also shown variations in PSA levels according to genetic factors, obesity, certain medications, and standardization bias, adding to the complexity of its interpretation     . Despite these issues, there is general consensus that widespread PSA screening has led to a striking stage migration, with the vast majority of prostate cancers now diagnosed at a localized stage . "
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ABSTRACT: Prostate cancer screening is highly controversial, including the age to begin prostate-specific antigen (PSA) testing. Several studies have evaluated the usefulness of baseline PSA measurements at a young age.
Review the literature on baseline PSA testing at a young age (≤60 yr) for the prediction of prostate cancer risk and prognosis.
PubMed was searched for English-language publications on baseline PSA and prostate cancer for the period ending April 2011.
In most published series, median PSA levels in the general male population range from approximately 0.4 to 0.7 ng/ml in men in their 40s and from approximately 0.7 to 1.0 ng/ml in men in their 50s. Evidence from both nonscreening and screening populations has demonstrated the predictive value of a single baseline PSA measurement for prostate cancer risk assessment. Specifically, men with baseline PSA levels above the age-group-specific median have a greater risk of prostate cancer diagnosis during the next 20-25 yr. Additional studies confirmed that higher baseline PSA levels at a young age are also associated with a greater risk of aggressive disease, metastasis, and disease-specific mortality many years later.
Baseline PSA measurements at a young age are significant predictors of later prostate cancer diagnosis and disease-specific outcomes. Thus baseline PSA testing may be used for risk stratification and to guide screening protocols.
Available from: Carlos Rubio-Terrés
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ABSTRACT: A pharmacoeconomic analysis was carried out comparing the efficacy of two treatment options for community-acquired pneumonia (CAP): telithromycin and clarithromycin. It was a retrospective analysis using a decision tree model. The efficacy of the two treatment options was estimated from a randomized, double-blind clinical trial, in which 800 mg/day oral telithromycin for 10 days was compared to 1000 mg/day oral clarithromycin for 10 days in patients with CAP (162 and 156 respectively). The use of resources was estimated based on the clinical trial and Spanish sources, and the unit costs from a Spanish health costs database. Costs were evaluated for the acquisition of antibiotic treatments, change of antibiotic due to therapeutic failure, hospital admissions, adverse reactions to treatment, primary care visits, tests and indirect costs (working days lost). The model was validated by a panel of Spanish clinical experts. As the clinical trial was designed to show equivalence, there were no significant differences in efficacy between the treatment options (clinical cure rate 88.3% and 88.5%, respectively), and a cost minimization analysis was performed. In the base case, the average cost of the disease per patient was 308.29 euros with telithromycin and 331.5 euros with clarithromycin (a difference of 23.21 euros). The results were stable in the susceptibility analysis, with differences favorable to telithromycin ranging between 5.50 and 45.45 euros. Telithromycin results in a cost savings of up to 45.45 euros per CAP patient compared to clarithromycin.
Available from: Claus G Roehrborn
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